There is a locking device for an auxiliary lock of U.S. Pat. No. 5,010,749, which comprises a rotatable ring and a base. The ring is fitted around the auxiliary lock and combined with the base. Then they are mounted in the door to let a large part of the rotating ring be exposed outside the door, and rotating the ring can cause the dead bolt of the auxiliary lock to extend out, locking the door.
However, a safety means is not accommodated in this device, so the rotating ring may be turned by mistake, locking the door without any intention to do that.